INVESTIGATION OF THE STRUCTURE AND WEAR RESISTANCE OF NITROOXIDIZED LAYERS

Abstract

Abstract: This study investigates the influence of plasma nitrocarburizing temperature on the microstructure, phase composition, microhardness distribution, and corrosion resistance of treated steel. Thermochemical treatment was carried out at temperatures ranging from 520 °C to 620 °C in order to analyze the formation mechanisms of the compound layer and diffusion zone. The results demonstrated that increasing the processing temperature significantly affected the development of γ′ (Fe₄N) and ε (Fe₂–₃N) phases, as well as the thickness and morphology of the compound layer. At 620 °C, an austenitic region was observed beneath the compound layer, indicating intensified diffusion processes and structural transformations. The maximum ε phase fraction was detected in samples treated at intermediate temperature, while the highest microhardness values were recorded within the central region of the compound layer formed at elevated temperature. A gradual decrease in hardness toward the substrate confirmed the presence of a structural gradient across the diffusion zone. Corrosion testing revealed that corrosion resistance is predominantly governed by the type, distribution, and morphology of carbonitride phases rather than by the total thickness of the compound layer. The findings emphasize that optimization of phase composition and surface characteristics plays a crucial role in enhancing functional performance.